While I don't know your local meta, 4 melta guns and 8 plasma guns doesn't seem like much anti tank for 1850 points. If your opponent brings av14, only the melta guns are going to be able to do anything against it, and they'll probably get focused on, and the plasma is almost as likely to kill your own unit as score a glancing hit on av13. Maybe see if you can get a lascannon heavy weapon team in or something.